The term "intelligent" or "smart" cards generally refers to information cards that contain integrated circuits (IC) for storing, retrieving, processing and transmitting information. These smart cards or IC cards find advantageous application in the fields of finance, commerce, transportation, communication, health and safety, and identification and security.
It is known to incorporate batteries into such cards to provide a power source for the electronic circuitry within. Having a battery incorporated into the IC card allows for the storage of greater amounts of data, and further allows for improved processing capabilities. As will be appreciated, the available space within an IC card is limited and requires an extremely thin power source. While it is known to incorporate batteries with IC cards, it has been difficult to actually reduce to practice an IC card having the thickness of an typical credit card, and at the same time, provide the energy requirements necessary for storing and retrieving large amounts of data. With the addition of more and more features of electronic devices to IC cards, the allottable space for a power source within the card becomes smaller and smaller. It is believed that with today's technology and with the desire to provide more and more features therein, the allowable area, or footprint, for a battery within an IC card (of conventional credit card dimensions) will tend to become less than about 25 mm by 35 mm. In addition, the thickness of the battery must be less than 1 mm to fit within conventional credit cards, which themselves are typically about 0.8 mm thick. With such constraints, it becomes more and more difficult to utilize batteries in conventional cylindrical or button cans and still provide the necessary energy and power. In addition, as more and more electronic capabilities are added to IC cards, the energy requirements will increase. Higher and higher electrical drain rates will thus tend to require larger and more powerful batteries, rather than smaller ones.
Because of the difficulty of providing the energy required within the space constraints of the credit card size, it is desirable to use the most energetic battery chemistries practicable. This is particularly important for secondary (rechargeable) batteries, because commercially-used secondary chemistries have, in general, lower energy content than commercially-used primary (non-rechargeable) chemistries. For example, lithium-ion chemistries have some of the highest energy densities among commercially available secondary systems, but still have considerably lower energy content than the most energetic primary battery chemistries, such as those based on lithium metal. Secondary electrode materials having higher energy content than the currently used materials are known, but have not been used in practice because of concerns about their safety, particularly their thermal stability.
The present invention overcomes these and other problems, and provides an IC card having as part thereof an ultra-thin, secondary battery having a flexible battery package.